Microbe-catalyzed processes are particularly useful in the production of a variety of chemicals known as fine or specialty chemicals. Perhaps the most important commercial use of microbe-catalyzed processes is in the food industry. Exemplary of such processes is the production of high fructose corn syrup (HFCS) catalyzed by immobilized glucose isomerase. This process converts glucose to an approximately equimolar mixture of fructose and glucose; this mixture is referred to as high fructose corn syrup.
The immobilization of an enzyme which catalyzes a microbe-catalyzed process generally gives better yields of desired product and preserves enzyme integrity. Basically, immobilization is the conversion of enzymes from a water-soluble, mobile state to a water-insoluble, immobile state. The immobilization of the enzyme can be done while the enzyme is still in the living microbe (intracellular), or when the enzyme is in the cell-free state; the immobilization techniques will vary in accord with these two enzyme states. Thus, it should be appreciated that immobilization conditions effective for intracellular enzymes will not necessarily be appropriate for extracellular enzymes, and vice versa.
The immobilization of intracellular enzymes is exemplified by the following U.S. patents:
U.S. Pat. No. 3,779,869--Glucose isomerase within bacterial cells can be stabilized by glutaraldehyde treatment. PA0 U.S. Pat. No. 3,935,069--Microbial cells are flocculated in the presence of certain metallic compounds. PA0 U.S. Pat. No. 3,980,521--Microbial cells are concentrated and crosslinked with glutaraldehyde to form a coherent solid product. PA0 U.S. Pat. Nos. 3,989,596; 3,989,597--Microbial cells having enzymes are subjected to flocculation conditions to produce whole cell aggregate which is useful in effecting enzymatic chemical transformations. PA0 U.S. Pat. No. 4,208,482--Microbial cells containing glucose isomerase are mixed with agar.